This invention concerns a U-shaped lock, particularly such a lock having reduced weight, and increased anti-theft function.
Conventional U-shaped locks generally include a body formed and operated with a single stage for locking and unlocking, and a U-shaped shackle inserted and locked therein. The shackle has one of its two ends always connected inseparably with the body, with the other end being separated from the body in unlocking. The lock unit pushes a pull rod unit to lock or unlock the shackle. Some U-shaped locks have shackles separable completely from the body when unlocked. The body is made of zinc alloy, aluminum, copper, etc. by a molding process and then its outer surface is treated. The lock unit, the pull rod unit and the shackle are then fitted in relative positions. The lock unit is generally locked or unlocked with one stage of operation for pushing and pulling the pull rod unit to lock or unlock the shackle.
However, the conventional U-shaped locks are deemed to have a drawback in that they are too heavy, even those made of zinc alloy, not to mention those made of copper. Another drawback is that the costs are high, not satisfying economic principles. One more drawback is that their anti-theft function is not so good, so that an experienced thief can easily unlock the lock unit, because of the one stage operation of locking and unlocking the lock unit.